From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vinod Koul Subject: Re: [alsa-devel] [PATCH v5 06/10] dmaengine: add API for getting dma controller's quirk Date: Wed, 14 Oct 2015 16:23:10 +0530 Message-ID: <20151014105310.GQ27370@localhost> References: <1442187923-5736-1-git-send-email-shawn.lin@rock-chips.com> <1442188139-6017-1-git-send-email-shawn.lin@rock-chips.com> <20151005153746.GG13501@vkoul-mobl.iind.intel.com> <56139289.7000005@rock-chips.com> <561629D6.9010702@metafoo.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Shawn Lin , Addy Ke , Heiko Stuebner , alsa-devel-K7yf7f+aM1XWsZ/bQMPhNw@public.gmane.org, linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Doug Anderson , Takashi Iwai , dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mark Brown , Olof Johansson , Sonny Rao , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org To: Lars-Peter Clausen Return-path: Content-Disposition: inline In-Reply-To: <561629D6.9010702-Qo5EllUWu/uELgA04lAiVw@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: On Thu, Oct 08, 2015 at 10:31:18AM +0200, Lars-Peter Clausen wrote: > > Basically I agree not to expose dma's quirk to slave controllers...But, the > > fact I mentioned on cover letter explain the reasons why I have to let slave > > controllers know that they are working with a broken dma. It's a dilemma > > that if we don't want that to be exposed(let slave controllers' driver get > > the info via a API), we have t add broken quirk for all of them ,here and > > there, which seems to be a disaster:( > > The problem with this API is that it transports values with device specific > meanings over a generic API. Which is generally speaking not a good idea > because the consumer witch is supposed to be generic suddenly needs to know > which provider it is talking to. > > A better solution in this case typically is either introduce a generic API > with generic values or a custom API with custom values, but don't mix the two. > > > > > I would appreciate it if you could give me some suggestions at your earliest > > convenience. :) > > In this case I think the best way to handle this is not quirks, but rather > expose the actual maximum burst size using the DMA capabilities API. Since > supporting only a certain burst depth is not really a quirk. All hardware > has a limit for this and for some it might be larger or smaller than for > others and it might be the same IP core but the maximum size depends on some > IP core parameters. So this should be discoverable. yes that makes more sense than adding quirks, exposing the right values which should be a readable property for driver will ensure it works on system with/without quirks -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html